Inorganic semiconductors, such as zinc oxide, cadmium sulfide and Se, have been recognized for years as useful photoconductive elements or components thereof in applications such as electrostatic imaging due to their high photosensitivity. Photoconductive elements are generally required to be in the form of high quality large area thin films. However, such films are difficult to fabricate from most semiconductors and the photoconductive properties of even these semiconductors are very sensitive to the presence of defects in their film forms. Consequently, only a few, specifically ZnO, CdS and Se have been developed into useful photo-conductive films. A useful review of such materials and applications is found in "Photoconductivity and Related Phenomena", edited by J. Mort and D. M. Pai, Elsevier Scientific Publishing Company, Amsterdam (1976), particularly pages 126-128 and 469-476 thereof.
The need for better, cheaper and more flexible photoconductors has focused investigation into polymeric materials as possible photoconductors, because of the relative ease of film fabrication. A variety of organic systems, such as polymers and compositions comprising low molecular weight organic compounds embedded in nonphotoconducting polymers, were found to have promising properties. Useful reviews of such materials are found in H. Hoegl, J. Phys. Chem., 69, 755-766 (1965) and "Electrical Properties of Polymers", edited by D. A. Seanor, Academic Press, New York (1982), pages 93-125. In spite of the many advances in organic systems, the need exists for organic systems which have photoconductive properties comparable to inorganic materials, because polymers are in general not as efficient as inorganics for photogeneration of charges.
Attempts to mix inorganic semiconductors and polymers by physical methods such as deposition are described by P. J. Regensburger, "Photochemistry and Photobiology", Pergamon Press, Volume 8 (1968), pages 429-440. However, these attempts were unsuccessful in that the disadvantages of each separate material, i.e., relatively low polymer photoconductivity and poor quality inorganic semiconductor structure, still exist.
PCT International Publication Number WO 90/09884 discloses compositions consisting essentially of a porous glass matrix, the pores of which comprise a III-V semiconductor, and optionally, a polymer; PCT International Publication Number WO 90/09885 discloses compositions consisting essentially of a porous glass matrix, the pores of which contain a semiconductor and a polymer; and W. Mahler, Inorganic Chem., Vol. 27, Number 3, 1988, pp. 435-436 discloses various methods of preparing small particle semiconductors in various rigid matrices, including ethylene/methacrylic acid copolymer. However, none of these compositions are known to be photoconductive.